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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH] Remove powerpc specific parts of 3c509 driver
Date: Wed, 20 Sep 2006 02:58:39 +0200
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: akpm@osdl.org, Stephen Rothwell <sfr@canb.auug.org.au>,
	ppc-dev <linuxppc-dev@ozlabs.org>, netdev@vger.kernel.org,
	jgarzik@pobox.com
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>> Sure, PCI busses are little-endian.  But is readX()/writeX() for PCI
>> only?  I sure hope not.
>
> It's defined for PCI and possibly ISA memory. You can use it for other
> things if you whish to, but "other things" are arch specific in any
> case.

Huh?  You're saying that only PCI and ISA are standardised busses?

>> It would make a lot more sense if readX()/writeX() used the  
>> endianness
>> of the bus they are performed on.
>
> No way ! Again, it's evil if such a simple thing start doing different
> things depending on random external factors.

That's your opinion, yes.

I'm saying it's *not* doing different things: in both cases it just does
the correct-endian access.  Also it doesn't depend on "random external
factors" -- they're not random factors, and not external either: it only
depends on the bus the access is done on.

> Different bus -> different accessor.

Then please rename readX()/writeX() to pci_readX()/pci_writeX().

>> Now you can say, use readl_be() or something similar, but that's a)
>> ugly,
>> b) error-prone, c) exponential interface explosion, d) ugly.
>
> I'd rather has an interface explosion than having black endian magic
> happening inside of the accessors.

Any comments on a), b) and d) as well?


Segher